For construction of an artificial satellite, a honeycomb sandwich structure formed of face skin materials made of fiber reinforced plastics and a honeycomb core, which is lightweight with high stiffness, is generally used. In particular, the honeycomb sandwich structure having high stiffness is used in a mission mounted structure.
However, thermal deformation occurs in the honeycomb sandwich structure due to a change in thermal environment on an orbit, such as sunlight heat input and heat generation of mounted equipment. Therefore, an angle of an Earth-oriented axis in mission equipment such as mounted camera and antenna varies. In particular, in a stationary satellite located about 36,000 kilometers away from the Earth, even a slight variation in the angle of the oriented axis significantly lowers accuracy of Earth observation and positioning.
Therefore, it is important to maintain a temperature of the honeycomb sandwich structure as uniform as possible through thermal control using a heater or the like so as to suppress the thermal deformation. It is also necessary to measure the temperature of the honeycomb sandwich structure on the orbit with high resolution and high accuracy so that precise thermal control is implemented.
As one of sensors for evaluating a temperature of a structure made of fiber reinforced plastics or other plastic, an optical fiber sensor has been proposed. The optical fiber sensor is a small-sized lightweight temperature sensor, and is sometimes used in a state of being embedded in the structure or in a state of being bonded to a surface of the structure.
As one of the above-mentioned structures including the optical fiber sensor, there exists, for example, an artificial satellite equipment panel having a surface on which an optical fiber sensor including a fiber Bragg grating (FBG) that changes the Bragg wavelength in a reflectance spectrum in accordance with the temperature is bonded. Specifically, in order to measure a temperature of mounted electronic equipment and a temperature of an equipment panel present immediately therebelow, the optical fiber sensor is bonded to a surface of the equipment panel corresponding to a position at which the electronic equipment is to be mounted (see, for example, Patent Literature 1).